Demonstrating an active vibration isolation system

ABSTRACT

Active vibration isolation (AVVI) systems are becoming more available in various markets, one such market being vehicle operator seating. Unfamiliarity with the performance of such systems may cause users initial perceptions of system performance to be unfavorable. AVI systems can include a demonstration system capable of providing simulations too users of various types of vibration isolation systems under various input conditions, so that users can be introduced to the system benefits over other systems before using an AVI equipped product in its intended application.

BACKGROUND

Active vibration isolation systems are becoming more available invarious markets, one such market being vehicle operator seating. Thesesystems typically replace passive isolation systems. Users of products,systems, etc. that employ active vibration isolation systems may beunfamiliar with active vibration isolation technology, the benefits itprovides, how it operates, and what the user should expect from it. Thisunfamiliarity may cause a user's initial perception of systemperformance to be unfavorable.

SUMMARY

All examples and features mentioned below can be combined in anytechnically possible way.

In one aspect, a method for demonstrating an active vibration isolationsystem configured and arranged to isolate a suspended plant from avibration disturbance includes a first outputting by the activevibration isolation system actuator of a first time domain force to thesuspended plant to cause motion of the suspended plant that simulatesmotion the plant would experience if a predetermined vibrationdisturbance was applied and the plant was suspended with a passivesuspension comprising a spring and damper; a second outputting by theactive vibration isolation system actuator of a second time domain forceto the suspended plant to cause motion of the suspended plant thatsimulates motion the plant would experience if the same predeterminedvibration disturbance was applied and the plant was suspended with anormally functioning active vibration isolation system; wherein thefirst and second outputting can occur in any order.

Embodiments may include one of the following features, or anycombination thereof. The active vibration isolation system is capable ofoperating in either a demonstration mode or a normal function mode andthe active vibration system is installed as a component of a largersystem, the active vibration isolation system being prevented fromoperating in a demonstration mode when the larger system is ON. Thesecond outputting occurs within a short time period after the firstoutputting concludes. The first outputting occurs within a short timeperiod after the second outputting concludes. The second outputtingoccurs within 10 seconds of the first outputting. The first outputtingoccurs within 10 seconds of the second outputting. The second outputtingoccurs immediately after the first outputting. The first outputtingoccurs immediately after the second outputting. Information identifyinginformation the time domain forces is communicated to a user of theactive vibration isolation system. The active vibration isolation systemactuator outputs a force that causes radiation of an acoustic signalaudible to a user of the active vibration isolation system, tocommunicate the identifying information to the user. The activevibration isolation system is configured to isolate a seating surface ina vehicle from motion of the vehicle body.

In another aspect, a method for providing audible sound and outputmotion in an active vibration isolation system includes providing by theactive vibration isolation system an audio signal, commutating the audiosignal to provide commutated audio output signals, providing by theactive vibration isolation system a motion command signal, commutatingthe motion command signal to provide commutated motion output signals,and combining the commutated audio output signal and the commutatedmotion output signal to form a commutated combined output signal forprovision to individual phases of a multiphase actuator, tosimultaneously provide output motion and audible acoustic signal.

Embodiments may include one of the above and/or below features, or anycombination thereof. The audio signal is pre-filtered to compensate forrejection of a current feedback loop used as part of the activevibration isolation system. The total harmonic distortion of the audibleacoustic signal is less than 10%. The active vibration isolation systemis configured and arranged to isolate a suspended seat from a vehicularvibration disturbance.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a high level block diagram of an AVI system.

FIG. 2 is a block diagram showing how an audio signal can be input intoan AVI system for playback by the AVI system.

FIG. 3 is a logic flow diagram of the turn on logic of an AVIdemonstration system.

FIG. 4 is a logic flow diagram of the turn off logic of an AVIdemonstration system.

FIG. 5 is a perspective view of skirts for an AVI application in avehicle seat.

FIG. 6 is a block diagram representation of control functions in an AVIdemonstration system.

DETAILED DESCRIPTION

This disclosure relates to a self-teaching active vibration isolation(AVI) device. The following discussion will be made in the context ofapplication of AVI technology to a vehicle seat. An AVI system forvehicle seating is disclosed in U.S. Pat. No. 7,983,813, which is hereinincorporated by reference in its entirety. However, it should beunderstood that the embodiments described herein may also be used in anyother vibration isolation application where AVI technology may beapplicable, and are not limited solely to seating applications. Theembodiments disclosed herein are of particular benefit in vibrationisolation applications where a human being is exposed to the isolatedmotion.

New technologies such as AVI can often be hard for a user unfamiliarwith the technology to adapt to. Without a thorough understanding of thebenefits and the effects of the technology on the resulting motion of aproduct incorporating AVI, a user may often reject such technologybefore experiencing the product for a long enough time to realize thebenefits. In an application such as a vehicle seat for use in over theroad trucking where the vehicle incorporating an AVI seat may havemultiple users that vary over time, education methods such as use ofuser manuals, on line training and the like do not effectively transferthe needed understanding.

One way to educate drivers to understand how the product works and whatits benefits are is through having a built-in demonstration and trainingcapability, which for ease of description will be referred to throughoutthis disclosure as a demonstration system. The implementation of ademonstration system in an AVI application such as vehicle seating canleverage the systems existing components, including: the processor andcontroller, actuator and sensors, etc. These components can beprogrammed to produce simulated experiences, voice communication, soundsand motion that can be used to provide a high impact understanding ofhow the system works and what its benefits are, as well as provide anyother key messages that are important for the end user. The componentsof a typical AVI system will be described in more detail in a subsequentsection.

A typical AVI system includes an actuator of some type that can be usedto output arbitrary forces, and a controller that is used to determinewhat forces should be output by the actuator. In a typical vibrationisolation application, the goal is to reduce or minimize the vibrationof some payload. For example, the goal of the controller may be toreduce the acceleration experienced by the payload to zero, or to somearbitrarily small value. In practice, a controller will have a referenceinput for acceleration and a reference input for position, and thecontroller will control motion of the payload to drive payload motion tothe reference values. A typical system may use either a feedback orfeedforward topology (or a combination thereof) and some control law todrive the output vibration to a desired state (reflected by thereference values). In normal use, the reference value for accelerationwould be set to zero, and the position reference would be set to be themidpoint of the isolation system travel.

The same system components used to drive payload motion to the referencevalues described above can be used in a demonstration mode to conformthe payload vibration to follow an arbitrary vibration signature. Thegoal of the controller will be to drive the error between motion of thesystem output (motion of the payload) and the intended vibrationsignature to a minimum value, as opposed to driving total motion to aminimum value. This accomplished by providing to the reference inputsthe arbitrary vibration signature it is desired for the payload tofollow.

By providing the ability to force the payload of the AVI system tofollow an arbitrary vibration signature, the demonstration system cansimulate the behavior of various systems and conditions. The user can beprovided an experience that faithfully represents what would beencountered by virtually any isolation system (either passive, semiactive or fully active), even when such a system is not present. Ademonstration system incorporated as part of an AVI equipped device asdescribed herein can simulate how a wide variety of possible isolationsystems would perform for a wide variety of possible operatingconditions. A demonstration system as described herein can simulate howa wide variety of different isolation systems respond to the exact sameinput excitation, so performance of the various simulated systems underthe same operating condition can be directly compared by the user. Ademonstration system as described herein can present simulations ofdifferent isolation systems in whatever order is desired by the designerof the demonstration.

A demonstration system as described herein can present simulations ofdifferent isolations systems in rapid succession, with whatever timedelay between presentations is desired by the designer of thedemonstration. Various simulations can be provided essentiallyimmediately one after the other, with a time short delay betweenpresentations such as a few seconds, (which for example can anywherebetween 1 second and 10 seconds), or with as much time in betweenpresentations as is desired. For example, an explanation of a simulationmay be provided in between presentation of simulations, which may causethe designer to increase the time delay between the simulationspresented. Alternatively, explanations can be provided synchronous withthe provision of the simulation, and the time delay between differentsimulations can be minimized. It should be understood that the timebetween simulations is not limited in any manner, and can be chosen bythe designer to be whatever is desired, including zero time delay.

The ability to provide simulations of different systems encountering thesame disturbance, the same system encountering different disturbances,or combinations thereof in rapid succession is beneficial in allowing auser to understand the benefits of one system over another.Psychophysical comparisons benefit from reducing the time between theexperiences to be compared. It is generally difficult for humans toremember in detail the qualities of sensory experiences (how bumpysomething feels, what something sounds like, etc.) as time progresses. Ademonstration system as described herein allows comparisons of sensoryperceptions to be made in rapid succession which avoids the problem ofuser memory of the experience fading with time. In the case of comparingvarious vehicle seating systems, a comparison of different simulatedseat vibration isolation systems encountering the same section of roadcan be done in a far shorter period of time than would be required ifphysical systems had to be swapped in and out of the same vehicle andthe vehicle subsequently driven over the same section of road.

The system designer can choose what simulations to provide to a user tobest highlight the performance abilities of a fully active vibrationisolation system relative to other isolations systems which the user maybe familiar with. In one example of a demonstration system incorporatedinto AVI seat useful for over the road trucking, a demonstration systemmight first simulate how a passive suspension comprising a traditionalspring and damper arrangement (such as that provided on an AdmiralSeries Model: 40049 Air Ride seat, available from National Seating whichis part of CVG, Commercial Vehicle Group headquartered in New Albany,Ohio) responds to a predetermined vibration input that the seat wouldexperience when a truck incorporating the passive suspension seatencounters a road disturbance. Such a simulation can be generated byrecording the actual motion (acceleration and position of the seatingsurface) of a passive suspension seat as the truck in which it ismounted traverses a section of road. Alternatively, a measurement oftruck floor motion that occurs when a particular road disturbance isencountered can be recorded and stored for playback on a controllablevibration platform. A passive suspension seat can be mounted on thecontrollable platform, and the platform caused to vibrate in a manneranalogous to the recorded floor motion. The subsequent motion(acceleration and position) of the suspended portion of the passivesuspension seat can then be recorded. This recorded passive suspensionseat vibration signature is then used by the demonstration system as thetarget vibration signature for the first simulation. The recordedacceleration and position signatures are used as reference inputs to thecontroller. The AVI system will control the payload to follow thereference inputs (the passive suspension seat acceleration and positionsignatures). In this way, a user sitting in the AVI seat wouldexperience what a user would experience in a truck outfitted with apassive suspension seat as it traversed the section of road where theoriginal recording of truck floor vibration was obtained.

A subsequent simulation can then be provided to the user. In thissimulation, the behavior of the AVI equipped seat will be simulated forthe same operating conditions as for the passive suspension seatsimulation previously presented. Note that while it is possible toprovide simulation of a different section of road (or even the samesection of road encountered at different speeds) from what was simulatedfor the passive isolation system, the true differences between systemsis more observable when the same road disturbance traversed by the sametruck driven in the same manner is simulated. The simulation for the AVIseat can be carried out in an analogous fashion to what was describedfor the passively suspended seat. In this case, the AVI seat would bemounted to the same vibration test platform and the platform caused tovibrate in a manner analogous to the same truck floor vibrationsignature as was done previously for the passive suspension seat. Inthis case, the AVI seat mounted to the vibration test platform would beconfigured to operate in its normal operating mode (in general with itsreference acceleration input set to zero and reference position inputset to be the midpoint of suspension travel), and motion (accelerationand position) of the suspended portion of the AVI seat system would berecorded. This recorded AVI seat motion signature would be used in theAVI seat simulation, where the demonstration system would cause the AVIequipped seat to vibrate in a manner analogous to the recorded AVI seatvibration, by applying the recorded acceleration and position signaturesto the acceleration and position reference inputs of the controller.

In addition to providing simulations of various systems, a demonstrationsystem may provide additional information to the user. For example, thesystem may playback voice recordings that describe the demonstration.The recordings may describe the various simulations before, during, orafter they are provided to the user. The recordings can point outvarious aspects of performance the user should pay attention to in orderto maximize the effectiveness of the demonstration. The recordings mayprovide other information such as an explanation of the function ofsystem controls, or any other information which may be desirable toprovide to the user.

An AVI equipped device incorporating a demonstration system as disclosedherein can provide a demonstration to users and potential users of thedevice when the device is installed in its intended application. For thecase of an AVI equipped vehicle seat for use in over the road trucking,the demonstration can be provided to a driver of the truck when seatedin the truck itself, just prior to driving. A separate facility is notrequired to provide the various system simulations disclosed, the endproduct itself is capable of simulating numerous different systems andoperating conditions. The simulation capability used in thedemonstration system can be provided using essentially all of the samehardware the AVI equipped device uses for its normal function ofvibration isolation. A demonstration system included within an AVIequipped device as disclosed herein provides a convenient, costeffective method for demonstrating the benefits of AVI technology tousers of the devices incorporating the AVI technology, at the locationof and time when the devices are used.

A high level block diagram of a typical AVI system is shown in FIG. 1.This figure omits many details of AVI systems, but is useful tounderstand the functional blocks incorporated in an AVI system that canbe used for the demonstration system. Vibration isolated system 10comprises the AVI system 20 and the payload to be isolated 30. AVIsystem 20 comprises an I/O port 11, a processor 12, amplifier 14, memory15, actuator 16, and sensors 17. I/O port 11 provides an interface forcommunicating with the AVI system. The I/O port can provide whateverconnectivity a system designer wishes to include. It may consist ofwired interfaces such as USB, Ethernet, Fire Wire, HDMI, or any otherdesired hardware interface. A wireless connection to the system using aprotocol such as Bluetooth, Zigbee, one of the variants of IEEE 802 orsome other wireless protocol is also possible, and may be used inconjunction with or in lieu of a hard wired connection. I/O port 11 mayalso provide a plug in socket for portable data storage devices such asUSB thumb drives, SD cards, etc. I/O port 11 is used to provide amechanism to input information into the AVI system and/or outputinformation from the AVI system.

Processor 12 is connected to memory 15, I/O port 11, and has variousother I/O connections such as the connection to amplifier 14 and sensors17. A processor may have other I/O as well, such as ports for any otherperipheral devices that a designer may choose to incorporate. Theprocessor 12 can receive information directly from I/O port 11 or mayretrieve information from memory 15 or from other peripheral devices. InFIG. 1, controller 13 is shown as being contained within processor 12.Controller 13 determines forces required to be output by actuator 16 andissues current commands to amplifier 14 which applies the necessarycurrent (or currents for a multi-phase actuator) to actuator 16 to causeit to output the required force. In FIG. 1, controller 13 is shown as aprocess that can run on processor 12 and resides within processor 12.However, controller 13 could also be implemented as a separate physicalcontroller that communicates with processor 12 as needed. Sensors 17sense motion of the suspended plant, or structures that move with thesuspended plant. Though not shown, sensors for sensing the vibration ofthe structure the AVI system is designed to isolate its payload from(such as the vehicle floor in an AVI vehicle seating application) mayalso be included. In the case of an AVI seat, sensors 17 may sensemotion of the frame of the seat top, or they may sense motion of thearmature of the actuator that is coupled to the suspended plant. Sensors17 provide information about the motion of the isolated portion of thesystem back to the controller 13 and also back to amplifier 14.Controller 13 uses information from the sensors to compute requiredforces and current commands. Amplifier 14 uses the output from sensors17 as part of commutation processes 200 and 210, as shown in FIG. 2.

Amplifier 14 has a vibration current input and an audio current input.The vibration current input accepts the current command provided bycontroller 13. The audio current input will be discussed in more detailin a subsequent section. It should be noted that although the amplifier14 is shown as being separate from controller 13 and processor 14,portions of amplifier 14 may actually reside within controller 13 orprocessor 14. For example, the commutation process shown in FIG. 2 mayactually be performed within processor 12. It should be understood thatthe embodiments disclosed are not limited in the particular architecturechosen for the processing carried out by the various components.Separate processors or controllers may be used for various computationtasks, or a central processor with sufficient processing power can beconfigured to accomplish all required processing tasks.

The demonstration system provides the capability of storing and playingback a custom audio recording. In some cases, an AVI system such as anAVI seat may be purchased by a company for use by numerous employees,contractors, and the like. The company may wish to record a message forplayback to users of the system. A software utility can be provided thatallows a recording, such as a WAV file (or any other commonly availableformat for storing audio recordings in digital form, such as MP3, MP4,etc.) to be recorded on a personal computer, smart phone, MP3 player, orother known recording device, for download via I/O port 11 into the AVIsystem electronics unit.

In some instances, the message can be played to the AVI system user uponor just prior to commencement of the demonstration. In some instances,control over when a message is played can be provided to the purchaserof the system or a designee thereof, so that they can have the messageplayed at the beginning of a demonstration, at the end, or at any timethe system is first activated. In general, for safety reasons it ispreferable to limit audio communication of information to the user fromthe AVI system to those times when the normal vibration isolationbehavior of the AVI system is not required. However, it should beunderstood that the embodiments described herein are not limited in anyway in the times at which an audio message can be played back throughthe system to the user. For example, in some embodiments the audiocommunication ability of the system may be used to communicate an alertor fault condition or other system status information to the user whilethe system is in normal operating condition. The system can outputaudible signals communicating information about the status of othervehicle systems, or can be used for whatever purpose a designer wouldconsider using audible output in a vehicle for. It should be understoodthat the embodiments disclosed herein are not limited in any way to onlycommunicating audible information associated with a demonstration. Thedemonstration system can output signals that cause seat vibration, andcan simultaneously output signals that cause radiation of acousticsignals that can be perceived by the user. Radiation of acoustic signalswill be described in more detail in a subsequent section.

In addition to allowing the purchaser of the seat to record a messagethat can be played back through the AVI system, pre-recorded messagescan also be included as part of the demonstration system. In this way,the system can explain to the user what they are about to experience.The recorded messages can provide whatever information the manufacturerof the AVI system wishes to convey to the user. Messages can be used todescribe the function of the demonstration system, such as whatcondition is being experienced and what seat performance is beingsimulated. Recordings can provide tutorial information on how to operateseat functions. Recordings are not limited in the information they maycontain and convey to the users.

To ensure that the presence of a demonstration mode does not compromisethe safety of the normal operation of the system, control logic isimplemented for starting and stopping the demonstration mode. Thedemonstration system should only be operable under certain conditions.Flow charts of demonstration system operation are provided in FIGS. 3and 4. While the flowcharts in FIGS. 3 and 4 and the description thereofare made in the context of an AVI seat used in an over the road truckingapplication, the logic and flow charts are applicable to any otherdesired use for an AVI system that may be integrated into some otherlarger system or device.

The demonstration mode is only allowed to be active if it is determinedthat the truck is OFF. This keeps the normal AVI system operation andthe demonstration operation separate. As shown in FIG. 3, adetermination at 300 is made whether or not the truck is OFF. If thetruck is determined to be OFF, then the system looks for a transition ofthe AVI system power switch state from OFF to ON at step 301. If such astate transition is detected the demonstration starts; otherwise thesystem remains in standby mode 305. The system will start thedemonstration when all of the following conditions are true: The truckis OFF, and; the user rocks the product's power switch from OFF to ON(edge triggered). Edge triggering is required because it is desirablefor the AVI equipped seat to power itself off when the engine is shutoff during the course of normal vehicle operation, thus leaving the AVIsystem power switch in the ON position. At determination 300, if thetruck is determined to be ON, then the state of the power switch on theAVI system is determined. If the AVI system power switch is also ON,then the AVI system turns on in its normal mode of operation. If the AVIpower switch is OFF, then the system reverts to standby.

FIG. 4 shows the logical operation associated with ending thedemonstration. At 400, the demonstration is running. At 401, the stateof the power switch on the AVI system is observed. If the AVI systempower switch is switched to OFF, the demonstration is terminated and thesystem goes into standby 405. If the AVI system power switch remains ON,the state of the truck is observed at 402. If the system determines thatthe truck has switched ON, then the demonstration is terminated and thesystem goes to standby 405. If the truck remains OFF, a user interactiontimer is observed at 403. If the timer times out, then the demonstrationis demonstration is terminated and the system reverts to standby 405. Ifthe timer has not timed out, the system observes the state of thedemonstration at 404. If the demonstration has completed, the systemgoes to standby 405. If the demonstration has not completed, thedemonstration continues to run and the system is in state 400. The AVIsystem will end the demonstration and return to standby mode under anyof the following conditions: the user rocks the AVI system power switchto OFF; the truck is turned ON; the demonstration reaches completion;the user stops interacting with the system for a predefined period oftime (this ensures that the AVI system does not deplete the battery ofthe system Vehicle in which it is installed if the system (vehicle) isnot operating.)

It was mentioned previously that the demonstration system may outputaudible acoustical signals to communicate information to the user. Insome embodiments, it is possible to have the AVI force source 16generate the acoustic signals that convey information to the user. Thisremoves the need to include a separate audio output subsystem in an AVIdevice. However, the invention is not limited solely to providing audiooutput via the vibration isolation force source. It is also contemplatedherein that a separate audio subsystem may also be used to communicationaudio information to a user.

In general, it is only possible for the AVI system actuator 16 toprovide an intelligible audio output if the AVI system uses an actuatoras a force source that has sufficient bandwidth to provide useful outputenergy in the audible frequency range. Typical AVI systems designed forvibration isolation are generally designed to control vibration in afrequency range that is below the audible frequency range, or may onlyextent a short way into the audible frequency range, up to say 50 Hz orso. Such systems typically have not been designed with the intent ofproviding information such as intelligible speech as an output. In orderto accomplish this, a force source with bandwidth sufficient to provideintelligible speech is required, such as an electromagnetic actuator.Electromagnetic actuators useful for this purpose may be linearactuators or rotary actuators. Hydraulic actuators are generallyunsuitable for this purpose because they lack sufficient bandwidth.

In addition to requiring a force source with sufficient bandwidth, thecontrol electronics for the AVI system must have an input where an audiosignal intended for reproduction can be injected. The signal path fromthe input audio signal to force output of the actuator should havesufficient fidelity in order to output an acoustic signal of sufficientquality to provide intelligible speech output. In general, the systemshould be able to output a force into the seat structure up to as highas 4 KHz, preferably up to 5 KHz or greater, with good fidelity. Theresulting acoustical output signal should in general have sufficientlylow distortion such that a voice signal is clearly audible andintelligible. This can be accomplished with an acoustical signalgenerally having THD less than 10%, preferably less than 5%, and ideallyless than 1%.

In addition to having a actuator capable of outputting force withbandwidth sufficient to generate intelligible speech (for example up to4 to 5 KHz) and having a signal path in the AVI system electronics thatcan accommodate an audio signal input that also provides sufficientfidelity from audio signal input to force output (again with a bandwidthextending up to 4 or 5 KHz or greater), the AVI system must have astructure coupled to the AVI force source capable of receiving the forceoutput of the actuator and radiating sound to the environment in whichthe AVI system is located with sufficient efficiency such that the audiooutput is loud enough to be heard by the user. This requires that aradiating structure which is an efficient acoustical radiator bemechanically coupled to actuator in a manner such that force output fromthe actuator 16 is transferred to the radiating structure. To be anefficient radiator, the system should have low mass and large area. Inthe case of an AVI system used in a vehicle seating application, thesequalities are fulfilled by the AVI system skirts, which are depicted inFIG. 5. The seat skirts in FIG. 5 are made up of bottom portion 501which is affixed to the AVI system frame that is directly coupled to atruck seat floor, and upper portion 502 that moves with the isolatedportion of the seat. The primary purpose of the seat skirt is to protectagainst intrusion of foreign objects into the space contained within theskirts where the AVI system components are located. In general, betterintrusion protection is provided by heavier skirts using thicker wallcross sections, whereas acoustic performance would be improved usingthinner wall cross sections (less mass) and material with lower internaldamping. Acoustic performance and mechanical characteristics necessaryto support the primary functionality of protecting the AVI systemelectronics from penetration may need to be traded off against eachother. In some embodiments, the wall thickness has been reduced 3 mm andstiffening ribs have been added to improve rigidity of the panels.

FIG. 2 provides additional detail showing how an audio signal can becoupled into an AVI system to drive a multi-phase actuator to produceintelligible voice quality while simultaneously providing a desiredmotion output. FIG. 2 depicts the electronics required to drive twoseparate phases of a three phase actuator. Describing two phases issufficient to completely describe the motor because current in the thirdphase can be unambiguously derived from the current in the first twophases.

A motion command signal is input to commutation block 200. Commutationblock 200 determines which phases of the multi-phase motor should havecurrent applied at any given time. The outputs of commutation block 200are two current command signals i_(a) and i_(b). A third phase currenti_(c) can be derived from the first two currents according to theequation:i _(a) +i _(b) +i _(c)=0

Ignoring commutation block 210 and summers 203 and 213 for the moment,currents i_(a) and i_(b) feed into two current feedback loops, one forphase A and one for phase B of the motor. At summer 201, the measuredcurrent present in phase B is subtracted from the commanded current forphase B to form an error signal that is input to compensator 202.Compensator 202 is chosen to achieve desired characteristics of thefeedback control loop, as is generally known in the control arts. Thoughmany control laws are possible for use in compensator 202, in oneembodiment a traditional PI controller is used. The output ofcompensator 202 provides a voltage signal for application to the phase Binput of electromagnetic actuator 230. In an analogous fashion, acontrol loop for phase is also shown comprised of elements 211, 212, and214. As its operation is the same as the loop for phase B alreadydescribed, it will not be described further.

The outputs of plants 204 and 214 (and a 3^(rd) plant not shown) areforces that are applied between the isolated portion of the system andthe vibration input it is desired to isolated the isolated portion ofthe system from. Motion of the mechanical system 216 is sensed bysensors (not shown in this figure, but shown as sensors 17 in FIG. 1)and fed back to commutation block 200 (and also block 201 which isdescribed further below). The commutation blocks use the positioninformation to determine how to apportion currents across the variousphases in order to obtain the desired total force output.

In addition to the motion control system just described, also shown inFIG. 2 are elements used to generate currents for application toelectromagnetic actuator 230 that represent an audio signal it isdesired for the system to radiate. The input audio signal is input toaudio pre-filter block 220. The purpose of pre-filter 220 is to providea compensation response to invert the signal rejection that the earlierdescribed current feedback loops will exert on the signal. In this way,the inherent disturbance rejection exhibited by the current feedbackloops is counteracted. Additionally, pre-filter 220 also providesequalization to correct for deviations in the system linear acoustictransfer function (deviations in the transfer function from audiocommand signal input to acoustical signal output in the vicinity of theintended listener) from a desired reference acoustic response. Thepre-filtered audio signal is then fed to commutation block 210 whichforms as outputs audio phase A and audio phase B signals (there is alsoan audio phase c signal not shown, as it is related to phase A and Bsignals in the same manner as was described for the commutated currentsassociated with the motion command signal). The audio phase A signal iscombined with the compensated i_(a) current output from compensator 212in summer 213 to form voltage signal Va, and the combined signal Va isthen applied to plant 214. Similarly, the audio phase B signal iscombined with the compensated i_(b) signal output from compensator 202in summer 203 to form voltage signal Vb, which is then applied to plant204.

FIG. 6 provides a logical arrangement of elements to control ademonstration system in an AVI system. Elements in common with FIG. 1are shown with the same reference numerals in FIG. 6. The demo Sequencer600, user interface 601, motion profile playback 602, and audio profileplayback 603 have been added. Memory 15 of FIG. 1 has been split intonon-volatile memory 15 a and volatile memory 15 b. The demo sequencer600 controls running of the demonstration. Demo sequencer 600communicates with and accepts input from UI 601. Demo sequencer 600issues commands to and communicates with memories 15 a and 15 b, motionprofile playback 602, and audio playback profile 603. The demo sequencer600 determines what signals are obtained from memory, at what time theyare retrieved from memory, and at what time they are passed by themotion profile playback too the motion controller, and at what time theaudio signals are passed from audio profile playback 603 to the motorcontroller.

The motion profile playback block provides the reference motion inputfor the AVI system comprised of the motion controller 13, motorcontroller 14 a, amp 14, sensors 17 and the payload. In someembodiments, both acceleration and position reference signals areprovided to the motion controller. In some embodiments, the relativeweights the controller applies to the acceleration and position inputscan be varied by the designer. In some embodiments, only a positionsignal may be applied. It should be understood that the embodimentsdescribed herein are not limited by the exact form of reference inputused by the system. Acceleration, position, velocity, either alone or incombination can be used as reference inputs, as long as the resultingoutput motion of the payload follows the desired vibration signature.

Motor controller 14 a combines the audio signal and motion signal into asingle current command (or a set of current commands for each phase)that is then provided to the amplifier 14. In FIG. 1, a separate motorcontroller was not shown. It was assumed that the functions of the motorcontroller were performed either in the amplifier 14, the controller 13,or split between them. In the embodiment of FIG. 6, a separate motorcontroller 14 a is shown because of the separate audio path provided. Inthis embodiment, commutation is performed within the motor controller 14a, though this function could also be moved into amplifier 14 as well.The output of amplifier 14 is a set of voltages that are applied to thevarious phases of actuator 16. Actuator 16 is coupled to payload 30, andmotion of payload 30 is sensed by sensors 17. Information representingthe motion of payload 30 provided by sensors 17 is fed back to motorcontroller 14 a to be used for commutation purposes, and to motioncontroller 13 to be used for control of output motion of the payload.

Embodiments of the systems and methods described above comprise computercomponents and computer-implemented steps that will be apparent to thoseskilled in the art. For example, it should be understood by one of skillin the art that the computer-implemented steps may be stored ascomputer-executable instructions on a computer-readable medium such as,for example, floppy disks, hard disks, optical disks, Flash ROMS,nonvolatile ROM, and RAM. Furthermore, it should be understood by one ofskill in the art that the computer-executable instructions may beexecuted on a variety of processors such as, for example,microprocessors, digital signal processors, gate arrays, etc. For easeof exposition, not every step or element of the systems and methodsdescribed above is described herein as part of a computer system, butthose skilled in the art will recognize that each step or element mayhave a corresponding computer system or software component. Suchcomputer system and/or software components are therefore enabled bydescribing their corresponding steps or elements (that is, theirfunctionality), and are within the scope of the disclosure.

A number of implementations have been described. Nevertheless, it willbe understood that additional modifications may be made withoutdeparting from the scope of the inventive concepts described herein,and, accordingly, other embodiments are within the scope of thefollowing claims.

What is claimed is:
 1. A method for demonstrating an active vibrationisolation system configured and arranged to isolate a suspended plantfrom a vibration disturbance comprising: a first outputting by an activevibration isolation system actuator of a first time domain force to thesuspended plant to cause motion of the suspended plant that simulatesmotion the plant would experience if a predetermined vibrationdisturbance was applied and the plant was suspended with a passivesuspension comprising a spring and damper; a second outputting by theactive vibration isolation system actuator of a second time domain forceto the suspended plant to cause motion of the suspended plant thatsimulates motion the plant would experience if the same predeterminedvibration disturbance was applied and the plant was suspended with anormally functioning active vibration isolation system; wherein thefirst and second outputting can occur in any order.
 2. The method ofclaim 1 wherein the active vibration isolation system is capable ofoperating in either a demonstration mode or a normal function mode andthe active vibration system is installed as a component of a largersystem, the active vibration isolation system being prevented fromoperating in a demonstration mode when the larger system is ON.
 3. Themethod of claim 1 wherein the second outputting occurs within a shorttime period after the first outputting concludes.
 4. The method of claim1 wherein the first outputting occurs within a short time period afterthe second outputting concludes.
 5. The method of claim 3 wherein thesecond outputting occurs within 10 seconds of the first outputting. 6.The method of claim 4 wherein the first outputting occurs within 10seconds of the second outputting.
 7. The method of claim 3 wherein thesecond outputting occurs immediately after the first outputting.
 8. Themethod of claim 4 wherein the first outputting occurs immediately afterthe second outputting.
 9. The method of claim 1 wherein informationidentifying the first and second time domain forces is communicated to auser of the active vibration isolation system.
 10. The method of claim 9wherein the active vibration isolation system actuator outputs a forcethat causes radiation of an acoustic signal audible to a user of theactive vibration isolation system, to communicate the identifyinginformation to the user.
 11. The method of claim 1 wherein the activevibration isolation system is configured to isolate a seating surface ina vehicle from motion of the vehicle body.